Rubicline is a very rare rubidium-rich member of the feldspar group, structurally related to microcline. It is prized by advanced mineral collectors for its distinct reddish to pinkish coloration resulting from rubidium substitution. It is primarily found in highly evolved granite pegmatites associated with other rare-element minerals.
Is this rubicline?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch rubicline with a known reference. Rubicline sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Rubicline leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Rubicline typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: red, pink.
- 5Look at form & habitCrystal system: triclinic. Typical habit: prismatic crystals.
Often confused with
Rubicline vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside rubicline
Minerals reported to co-occur with rubicline. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Rb)AlSi₃O₈
- Mohs hardness
- 6
- Density
- 2.58 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Prismatic Crystals
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-500 depending on crystal size and quality
Where rockhounds find rubicline
Classic worldwide localities
- San Diego County, California
- Madagascar
- Italy
Field-hunting tip
Look in granite pegmatites country — that is the host setting where rubicline typically forms. If you start seeing quartz, muscovite, albite in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify rubicline?+
Where is rubicline found?+
How much is rubicline worth?+
What rocks look like rubicline?+
What minerals are found with rubicline?+
What kind of rock does rubicline form in?+
What is rubicline used for?+
Find rubicline on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
